Natural gas lines carry natural gas from a natural gas extraction site (e.g., a natural gas field) to other locations where it may be stored, shipped, or consumed. For example, a natural gas line may carry natural gas to one or more fuel cell systems, which use the natural gas to generate electrical energy. One of the byproducts of a fuel cell system that uses natural gas as fuel is carbon dioxide. Carbon dioxide is a greenhouse gas. Thus, carbon dioxide should be sequestered rather than released into the atmosphere. In addition, natural gas lines may leak natural gas, which contributes to greenhouse gas emissions and other damaging effects to the environment.